Definition
The retroperitoneal space is the anatomical region situated posterior to the parietal peritoneum and anterior to the transversalis fascia of the posterior abdominal wall. It contains structures that are not covered by the peritoneal cavity but are enclosed within the posterior abdominal compartment.
Boundaries
- Anteriorly: Parietal peritoneum.
- Posteriorly: Transversalis fascia, vertebral bodies, and associated musculature (psoas major, quadratus lumborum).
- Laterally: The lateral confluence of the peritoneum with the posterior abdominal wall, extending toward the thoracolumbar fascia.
- Superiorly: Extends upward to the diaphragm, where the retroperitoneal space continues as the posterior mediastinum.
- Inferiorly: Communicates with the pelvic extraperitoneal space via the urogenital hiatus.
Contents
The retroperitoneal space houses several vital organs, vessels, lymphatics, and fasciae, including:
| Structure | Description |
|---|---|
| Kidneys | Paired retroperitoneal organs responsible for filtration of blood and urine formation. |
| Adrenal (suprarenal) glands | Endocrine glands located atop each kidney. |
| Ureters | Muscular tubes conducting urine from kidneys to the bladder. |
| Pancreas (body and tail) | Primarily retroperitoneal; the head is intraperitoneal within the duodenal loop. |
| Portions of the duodenum (2nd–4th parts) | Retroperitoneal segments of the small intestine. |
| Ascending and descending colon | Retroperitoneal portions of the large intestine. |
| Aorta and inferior vena cava (IVC) | Major arterial and venous vessels supplying the lower body. |
| Aortic and IVC branches | Including the renal arteries and veins, gonadal vessels, lumbar arteries, and veins. |
| Lymphatic structures | Retroperitoneal lymph nodes, cisterna chyli, and thoracic duct origin. |
| Connective tissue | Including the renal fascia (Gerota’s fascia) and the lateroconal fascia. |
Classification of Retroperitoneal Structures
- Primary retroperitoneal – Organs that develop and remain in the retroperitoneal space (e.g., kidneys, pancreas body/tail, ureters).
- Secondary retroperitoneal – Structures originally intraperitoneal that become retroperitoneal during embryologic development as their mesentery fuses to the posterior abdominal wall (e.g., ascending colon, descending colon, duodenum except the first part).
Clinical Significance
- Imaging: The retroperitoneal space is routinely assessed by computed tomography (CT) and magnetic resonance imaging (MRI) for pathology such as tumors, hemorrhage, infection, and vascular disease.
- Trauma: Retroperitoneal injuries may result from blunt or penetrating trauma, leading to hematoma formation, organ laceration, or vascular disruption. These injuries can be occult due to the space’s deep location and limited peritoneal signs.
- Neoplasms: Primary retroperitoneal tumors (e.g., liposarcoma, leiomyosarcoma, paraganglioma) and secondary involvement from metastatic disease are evaluated via imaging and often require multidisciplinary management.
- Vascular disease: Aortic aneurysms, dissections, and occlusive disease manifest within the retroperitoneal compartment and may present with back or flank pain.
- Infection and inflammation: Retroperitoneal abscesses can arise from perforated gastrointestinal organs, renal infection, or spread from adjacent structures. Prompt drainage and antimicrobial therapy are critical.
Surgical Approaches
- Retroperitoneal access: Direct retroperitoneal approaches (e.g., flank incision, laparoscopic retroperitoneoscopy) provide exposure to kidneys, adrenal glands, and vascular structures while minimizing intra‑peritoneal contamination.
- Transabdominal approaches: Employed when concurrent intra‑peritoneal pathology requires access; surgeons must mobilize the colon and peritoneum to enter the retroperitoneal space.
Anatomical Variants
- Variations in the position of the kidneys (e.g., ectopic, horseshoe kidney) alter the spatial relationships within the retroperitoneum.
- Accessory renal arteries are common and may traverse the retroperitoneal fat, influencing surgical planning.
References
- Standring, S. (2020). Gray’s Anatomy: The Anatomical Basis of Clinical Practice (42nd ed.). Elsevier.
- Moore, K. L., Dalley, A. F., & Agur, A. M. R. (2018). Clinically Oriented Anatomy (8th ed.). Wolters Kluwer.
- American College of Radiology (ACR) Appropriateness Criteria® – Retroperitoneal Masses.
This entry reflects current anatomical and clinical knowledge as of the latest peer‑reviewed sources.
